Before this patch I was able to get the dragonflight season 2 and 3 master achievements which gave me emerald mark of mastery (s3) and draconic mark of mastery (s2) which I could turn in to the tier vendors in the respective zones to get a piece of tier from that raid which was great for collecting transmog. Same for Dragonflight season 4 master, used this for gearing alts but now cannot get it on alts at all.
I think this is happening due to warbands, it says the season master achievements are completable by the alt I was on, they had never done heroic aberrus before (but they did heroic amirdassil and got season 3 master before this patch). I did heroic aberrus yesterday for the first time on that alt and not only didn’t get the heroic: Aberrus achievement, I didn’t get the dragonflight season 2 master achievement either. This kinda sucks because it was a good way to get tmog tier pieces from s2 and also a good way to gear up current alts with season 4 master.